1. Field of the Invention
The present invention generally relates to low k dielectric materials. More particularly, the invention relates to a process of depositing low k dielectric layers on a substrate.
2. Description of the Related Art
Integrated circuits with sub-micron features that are densely spaced on substrates have been created as the result of improvements in integrated circuit design and fabrication. The increasingly smaller features used on integrated circuits have increased the importance of reducing the dielectric constant of the many layers typically used in recent integrated circuits and reducing the capacitive coupling between features such as interconnect lines. Using materials in the insulating and non-conductive layers of integrated circuits which have a low k (dielectric constant<4.0) is one method of addressing these two concerns.
Several characteristics of known low k materials make them undesirable for use in semiconductor devices. Some low k materials, such as parylene, do not withstand the high temperatures used in processing substrates to make semiconductor devices. Other low k materials, such as porous silicon oxides, do not serve as effective barrier layers which are needed to prevent the diffusion of materials, such as water and metal ions between conductive and insulating layers of a semiconductor device. Some low k materials have been created by including dopants, such as fluorine, in a higher k film. However, the use of dopants may result in chemical bonds in the film which expose or damage photoresist materials that may be placed on top of the film in order to etch the substrate using photolithography.
Low k materials are also desirable for layers besides barrier layers. The dielectric constant of each layer in a substrate is important because each layer contributes to the overall dielectric constant of the device. Examples of other layers which preferably have a low k are etch stop layers, anti-reflective coatings, and hard masks.
Etch stop materials are typically materials that have a slower etching rate compared to a dielectric layer that is deposited on the etch stop.
Anti-reflective coatings are layers that are used to prevent reflections between substrate layers. Such reflections can reach and expose portions of the photoresists used in photolithography to etch substrates. Such unwanted exposure of photoresists results in unwanted substrate patterning.
Hard masks are masks which are used to pattern substrates. The hard masks are typically left as a layer of the substrate after they have been used for patterning.
There remains a need for a process to make low k materials which can be used as effective barrier layers, etch stop layers, anti-reflective coatings, and/or hard masks. Furthermore, there remains a need for low k materials which do not damage photoresist materials.